Hastelloy pitting resistance
Hastelloy pitting resistance describes the ability of Hastelloys to protect against local pitting in chloride-containing environments. This is especially important in highly acidic process environments.
Physical-Chemical Mechanism of Action
Hastelloy pitting resistance comes from the alloy's specific composition, especially nickel and molybdenum. These alloys form a dense protective layer on the surface that shields against chloride ions and prevents localized corrosion from starting.
Metallurgical Relevance & Welding Risks
If pitting resistance is poor, local pitting can occur in chloride-rich environments. This leads to cracks and can impair the mechanical strength of the components. Therefore, it is crucial that the weld has high pitting resistance.
Workshop Practice & Instructions
To ensure the weld has high pitting resistance, the following measures should be taken:
1. Use high-quality Hastelloy raw materials with the correct composition.
2. Make sure the weld doesn't cool too quickly during cooling (t8/5 > 25 s) to get a homogeneous structure.
3. Use suitable shielding agents and get familiar with the specific requirements of the Hastelloy grades you are using.